Telephone system



Dec. 31, 1929.

J. H. VOSS ET AL TELEPHONE SYSTEM Filed Dec. 1928 Full 0P 2 Sheets-Sheet l D62. 31, 1929. J. H. voss ET AL 1,741,746

TELEPHONE SYSTEM Filed Dec. 1928 2 Sheets-Sheet 2 [WET m1? ClarenceELnmax Juh'n U055 Patented Dec. 31, 1929 UNITED STATES PATENT OFF ICE JOHN H. VOSS, OF BZERWYN, AND GLARENCEE. LOMAX, OF

OAK FAKE; ILLINOIS, AS-

SIGNOBS T0 RESERVE HOLDING COMPANY, OF KANSAS CITY, MISSOURI, CORPORA- TELEPHONE SYSTEM Application filed December 3, 1928; Serial No. 323,428.

The present invention relates to telephone systems in general, being more particularly concerned with inter-exchange trunk lines in which special arrangements are provided to secure quiet transmission over such trunkby way of the grounded exchange battery and a retard coil or repeating coil winding. With inter-exchange trunk lines so grounded, the ground connections to the respective conductors of a trunk line must be of the same impedance and the trunk line itself must be well transposed over its entire length, in case it is subjected to alternating electro-statie influence due to the proximity of power lines and the like in order to secure undisturbed conversation. It has been found by test' that in case the ground connections are eliminated or removed during conversation that a qulet circuit can be obtained over a trunk line which would give interference with a ground connection. This fact has been recognized for some time and. circuits have been designed employing battery connections from a grounded battery to one end of the trunk line in order to furnish supervisory current and for other purposes during the setting up" of a connection, Witharrangements for auto matically removing the grounded battery connections during conversation. The circuits heretofore developed, so far as applicant is aware, have been circuits for use in! automatic telephone systems wherein. the trunk lines in question are seized by selector switches (switches employed to select other selectors or to select final connectors).

The main object of the present invention is the provision of circuit arrangements for automatically removing all ground connections during, conversation from an inter-exchange trunk line accessible at one end to final connectors and for so arranging the circuits that the usual supervision willv be givenby any connector calling the line so as to indicate to the calling party the calling party be an operator) when the called party answers and when he again hangs up.

The other objects as well as the several features of. the present arrangement will become apparent upon a further perusal of the specification in connection. with the accompanying drawings comprising Figs. 1 and 2.

The invention. has been embodied in this disclosure in connection. with two-way trunk lines to-v which calls are extended by way of rotary connectors in a main exchange and are received at an operators switchboard in branch exchange and are extended in the other direction from selectors in the branch. exchange over the trunk line and through first selectors-in the main exchange.

Referring now particularly to the drawings comprising Figs. 1 and 2, these drawings show by means offthe usual circuit diagrams a sufficient amount of equipment in a telephone system embodying the principles of the invention to enable the same to be understood. More in particular, these drawings show a trunk line TL extending between a main exchange and a private automatic exchange, the main exchange being assumed to be located in a city while the private automatic exchange is located in an industrial plant several miles away.

Fig; '1' shows the repeater R which is interposedbetwecn the trunk line TL and the connectors, such as the connector C, which have access to the trunk line to extend calls from the main exchange to the private auto matic exchange (abbreviatedP. A. The repeater R is interposed between the trunk line TL and the individual first selector S and it functions oncalls "from the P. A. X. to themain exchange to repeat impulses received over the trunk line to the selector SL, and to other automatic switches, to complete the connection.

The two-way repeater R is shown in Fig. 2 and it is interposed in the branch exchange between the conductors 150' and 151v of the trunk liineTL and the conductors 21()-215 over which connections incoming from the main exchange are extended to the local lines through the jacks J and NJ and through which connections from the local lines are extended to the trunk lines by selectors such as the selector S The selector S Fig. 1, and the selector S Fig. 2, may be similar to the selector E shown in Fig. 1 of Patent No. 1,349,381 issued to Emil Jacobsen, August 10, 1920, and the connector. C of the present drawings may have circuits similar to those of the connector H shown in Fig. 2 of the said patent to J acobsen.

In order that the invention be understood best, a detailed description of the operation r of the apparatus shown will now be given.

For this purpose, it will be explained first how a call is extended from the main exchange to the P. A. X. over the trunk line TL.

Call from the main exchange to the P. A. X.

In making this description, it will be as sumed that the connector C is taken for use over the conductors 101103 in the usual manner and is operated in accordance with the designation oi the trunk group containing the trunk line TL. The connector C operates in the manner explained in the Jacobson patent hereinbetore referred to to rotate its wipers 104106 over the bank termin of busy trunk lines in the group until it locates an idle one. Assuming that trunk line TL is idle, this fact is indicated by an ungrounded condition of the'release trunk conductor 108 thereof, and the test wiper 105 permits the wipers of the connector G to come to rest on the bank contacts associated with the repeater R the wipers 104 and 106 engaging bank contacts associated with the negative and positive trunk conductors 107 and 109, respectively. As soon as this connection is made, the connector 0 applies ringingcurrent to conductors V 107 and 109 in the usual manner. Upon seizing the trunk line extending to the repeater R the connector C places a ground potential on release trunk conductor 108 thereof by way of test wiper 105 in order to make the trunk line busy to the other connectors hav ing access to it. This results in a closure of a circuit over conductor 108 and through contacts of relay 131 of the repeater R for the transfer relay 112 which transfers the conductors 150 and 151 of the trunk line TL from the conductors leading to the repeater R? to the conductors of the repeater R Relay 112 also closes a circuit for the slow-to-pull-up relay 111 which operatcsits armature a slight interval after its circuit is closed. As a result of the connection of conductors 150 and 151 to the right-hand repeating coil windings of the-repeater R supervisory relay 110 of the repeater operates over conductors 150 and 151 in series from the battery feed connections normally applied to these conductors in the P. A. X. through the left-h and repeating coil windings of the repeater R by way of contacts of relay 203 and through the windings of the battery-feed relay 202, Upon operating, relay 110 opens a point in the shunt around the condenser associated with the left-hand repeating coil winding so that the operation of relay 111 as a result of the operation of relay 112 does not close the shunt around this condenser for the time being. The circuits in the repeater R are now in readiness to trip the ring-cut-oit relay in the connector C and to give answering supervision to the calling party upon the repsonse of the operator in the P. A. X.

In the P. A. X. the battery teed relay 202 pulls up over conductors 150 and 151 in selies with relay 110 of the repeater R and closes a circuit for the slow-acting relay 201. Relay 201 operates and at its upper armature places a ground potential on the local release trunk conductor 211, preparing other circuits at its other contacts. The ring-up relay 207, whose upper winding is connected across the inside terminals of the left-hand repeating coil windings through the associated eondenser 223 and its own contacts, as well as 0011- tacts or relay 205, operates in response to the ringing current received over conductors 150 and 151, repeated through the repeating coil in the repeater R from the connector 0. Upon operating, relay 207locks itself by means of its lower winding to the conductor 216 through its lower contacts by way of con tacts of cut-oft relay 203, conductor 216 being grounded at the lower contacts of relay 201. At its middle lower armature, relay 207 removes its upper winding from in shunt of the inner left-hand repeating coil terminals,

and at its inner lower armature it closes a circuit through contacts of the night relay 208 for the lamp L associated with the jack J.

Upon noting the lighted condition or" the lamp L the operator at the P. A. Xfinserts the plug of an idle cord circuit into the jack J, whereupon the upper contacts place ground on the hold conductor 214i, closii g a circuit for cut-01f relay 203. Relay 203 operates and re moves the battery feed relay 201 from in. connection with the trunk conductors 150 and 151 to the repeating coil winding, causing certain circuit changes to take place in the main or; change as will be hereinafter pointed out. Relay 203 also opens the locking circuit of ring-up relay 207, permitting this relay to fall back, and completes a locking circuit for relay 201, through the lower armature of relay 203 and the inner lower armature of relay 201. At its inner lower armature, relay 203 connects talking condenser 221 in parallel with talking condenser 222 so as to improve the talking quality of the circuit. It has been found that a better response of thering-up relay 207 is secured when the condenser 221 is left out of circuit during the ringing operation.

Line relay 204 operates through the operators cord, by way of the jack J and over conductors 210 and 215, and operates release relay 205. Relay 205 operates relay 206, which makes multiple ground connections to conductors 211 and 214.

In the main exchange, the removal of the battery and ground connections from conductors 150 and 151 of the branch exchange results in a deenergization of relay 110. Now, since relay 111 is operated by relay 112, relay 112 being operated over the grounded release trunk conductor 100, a shunt is now complete around the condenser connected between the inner left-hand repeating coil windings, and the ring-cut-otl relay (not shown) in the connector C is operated in the usual manner to stop the application of ringing current and to place the connector in talring condition. The same bridge across conductors 107 and 109 that trips the ring-cut-otl relay is effective to operate the usual baclebridge relay ot the connector so as to cause supervision to be given to the calling party.

The operator in the P. A. X. now converses with the calling party in the usual manner" and completes the connection by inserting the other plug of the cord circuit in use into a jack in which the desired line terminates. The operator signals the called line by throwing the ringing key in her cord circuit in the usua manner and when the called subscribe answers the conversation may proceed.

lVhen the conversation is terminated, the two parties involved therein hang up their receivers. lVhen the receiver is replaced at the calling substation, the connector in use is not released, but the preceding switches are released in the manner explained in the Jacobsen Patent 1,349,381, hereinbet'ore referred to. The connector inthe main exchange is of the release-by-last-party type and it holds the trunk guarded in the main exchange until it is permitted to release when the plug is withdrawn in the P. A. X.

The cord circuit in use in the P. A. X. is provided with the usual supervisory arrangement, giving the operator answering and disconnect supervision. When the P. A. X. operator receives the disconnect signal, she pulls down the connection. When the plug is removed from the ack J, line relay 204 falls back followed by the deenergization of the slow-acting release relay 205. When relay 205 tails back it removes the ground potential its lower armature from the holding conductor 214 whereupon cut-oft relay 203 falls back and reconnects battery feed relay 202 to the inner repeating coil terminals and opens the locking circuit of relay 201. Relay 202 now reoperates over the trunlrline and re closes the initial circuit of relay 201.

RelayllO in the repeater R Fig. 1, operates over the trunk line TL and opens the supervisory bridge across conductors 107 and 109 whereupon the release-by-last-party connector C releases in the manner described in the Jacobsen patent hereinbetore referred to, removing ground potential from release trunk conductor 108. Then this occurs, transfer relay 112 falls back and transfers the trunk line conductors to the repeater R whereupon the battery teed relay 202 of the repeater R falls back owing to the fact that the respective trunk line conductors are now connected to the same potential at both ends and no current flow takes place over the trunks at this time. Upon falling back, relay 202 opens the circuit of relay 201 and relay 201 falls back after a slight interval and removes ground from release trunk conduct-or 211 at its upper contact, rendering the trunk idle to the selectors such as the selector S Call from the P. A. X. to the main e wchomge In order to explain further the operation of the apparatus shown in the drawings, it will be assumed that a l A. X. subscriber removes his receiver and causes his usual line switch (not shown) to operate in the usual manner and seize a selector such as the se lector S Fig. 2. It will be assumed further that the P. A. subscriber desires a main exchange connection and that he accordingly dials the digit constituting the main exchange prefix, the digit 0 for example. WVhen this is done, the selector S raises its wipers opposite the desired level of bank contacts and seizes an idle trunk line, which trunk line,

it will be assumed, is the trunk line TL and represented in the selector banks by the contacts terminating conductors 210, 211, and

215. When this trunk line is selected, line relay 20 1 of the repeater R pulls up over the calling line through the selector S and over conductors 210 and 215 by way of contacts of relay 208 and the right-hand repeating coil windings. 204C closes a circuit tor release relay 205, which relay operates and places a ground potential on release trunk conductor 211, thereby closing a holding circuit for the selector S and the subscribers line switch. At its lower armature, relay 205 places ground on the holding conductor 21%, closing a circuit for cut-oil relay 203; Relay 208 operates and disconnects the inner left-hand repeating coil terminals from battery teed relay 202 and connects them together through an impulsing circuit including the inner lower armature, operated, of relay 203, upper contacts of line relay 20%, and the upper armature of relay 201.

In the main exchange, the line relay 130 of the repeater R which is connected to the inner right-hand repeating coil terminals through contacts of relays 129 and 127, energizes over the conductors 150 and 151 of the trunk line TL through contacts of the transfer relay 112 and through the left-hand repeating coil windings of the repeater R and Upon operating, relay 7 the impulsing circuit just traced including the upper contacts of line relay 204. Upon energizing, line relay 130 of the repeater R closes the usual circuit for the associated slow-acting release relay 131 with the result that relay 131 operates and shifts release trunk conductor 108 from in connection with transfer relay 112 to ground, rendering the trunk line TL busy to the connectors such as (1. Relay 13], also closes at its upper armature a circuit for the polarizing winding of the electropolarized relay 123. As a further result of the energization of line relay 130, a bridge is closed at the upper contacts of the line relay across the conductors 121 and 122 leading to the incoming first selector S This bridge includes the associated. left-hand repeating-coil windings and the upper winding of electro polarized relay 123 in series with the resistance 12 1. Current flows through this circuit from the line relay of the selector S which energizes with the usual result that the selector is preparer tor operation. Current is now floating through both windings of relay 123, but the relay is not operated at this time on account or the fact that the current flow in the upper winding, as indicated by the polarity signs associated with the upper winding, is in' the direction opposite to that in which it must flow in order to bring about an operation of the relay.

When the calling subscriber dials the first regular digit in the main exchange number, the main exchange prefix having been responded to by the selector S F 1g. 2, each interruption produced in the calling line by I the usual calling device results in a momentary deenergization of relay 10 1 of the repeater R which opens, at its upper armature, the circuit of line relay 130 of the repeater R with the result that each interruption in the calling line results in a momentary deenergization of line relay 130, which in turn interrupts the line circuit of the first selector S The selector S responds to this digit and selects an idle trunk line in the usual man ner. It will be noted that relay 206 of the repeater R operates'upon the first deenergization of line relay 20 1 and, being slow acting, remains operated throughout the digit. The operation of relay 206 results in the lower right-hand repeating coil being shunted in order to improve the impulsing circuit. Shuntingboth of the right-hand repeating coil windings may result in still better impulsing conditions, but the gain resultingtrom shunting a second repeating coil winding seems to be so small in comparison to the gain resulting from shunting one that it is thought that the arrangement shown in the drawings is the best, consideration being given to economy. in the repeater R the relay 132 bears the same relation to relays 130 and 131 as relay 206 of the repeater R does to the relays 204 and 205.

Relay 132 shunts the lower right-hand repeating-coil winding at its lower contacts and at its upper contacts it connects the in-, ner leftdiand repeating-coil terminals directly together to improve the impulsing conditions.

At the end of the digit, line relays 204 and 130 come to rest in an energized condition and relays 206 and 132 fall back.

The above action is repeated for each of the subsequent digits with the result that succeeding switches in the train are operated to set up the connection to the called line.

il hen the called subscriber responds, the connector in use causes a reversal in the direction of current flow in the talking conductors of the connection established thereto from the repeater R by way of the selector S whereupon the current flow in the upper winding of the electro-polarized relay 123 assists the current low in the polarizing winding in operating the relay. Upon operating, relay 121 places the condenser 125 in multiple with condenser 126 so as to improve the talking circuit and it closes a circuit at its upper contacts for the upper winding of the di'flierential relay 127. Relay 127 operates on account of the fact that there is no current flow through its lower winding at this time. Upon operating, relay 127 closes a holding circuit for the two windings of relay 130 through the lower winding of relay 129, disconnecting the two windings of relay 130 from the inner right-hand repeating-coil terminals, thus removing all local ground connections from the trunk line TL. Relay 129 operates through its lower winding and locks itself at its inner upper contacts to ground by way of the contacts of relay 1241. At its upper contacts, relay 129 opens a point in the circuit into which relay 130 was formerly energized, and at its lower contacts relay 120 connects the lower winding of dif ferential relay 127 between the inner righthand repeating-coil terminals by way of contacts of the electro-polarized relay 12 1.

The circuits remain in this condition throughout the conversation which may now take place.

Then the conversationis terminated, the two subscribers replace their receivers. For the purpose of explaining a certain feature of the invention, it will be assumed that the lays fall back and reconnect the windings of relay 130 to the inner right-hand repeating-coil terminals, whereupon relay 130 reoperates with the result that current flow is again resumed over the trunk line TL, relay 130 remaining operated. It the calling subscriber now reolaces his receiver, relay 130 falls back because the circuit thereof is opened at the upper armature of line relay 204: of the repeater it and the connection releases in the manner to be hereinafter described.

It will now be assumed that the calling subscriber replaces his receiver first, in which case relays 123, 127, and 129 (in addition to relays 130 and 131) in the repeater R are operated at the time the receiver is replaced at the calling station in the P. A. X. and there is no current flowing over conductors 150 and 151.

When line relay 204 of the repeater R falls back upon a replacement of the receiver at the calling substation it opens the connection across the inner left-hand repeating-coil terminals by way of contacts oi relays 201 and 203, but this is without effect at this time owing to the "fact that there is no current flowing over conductors 150 and 151, relay 180 of the repeater B being locked up locally by contacts ofrelay 127 through the lower winding of relay 129. A moment later, relay 205 falls back and removes ground from release trunk conductor 211 at its upper armature, permitting the selector S and the line switch in use to release, and at its lower armature it removes ground from conductor 21-1, whereupon cut-ofi' relay 203 restores and reapplies the two poles of the exchangebattcry,througl the windings relay 202, to the lIIIIGIlGIIHh nals of the left-hand windings of the asso ciated repeating coil. When this occurs, a cr rent flow takes place over conductors 150 and 151 and through the right-hand windings or the repeating coil in the repeater B through the lower winding of differential relay 127 by way of the lower contacts oi relays 12d and 129. The. diil'erential relay 127 restores when the opposingcurrent flow passes through its lower winding and at its lower armature connect-sthe lower Winding of relay 130 to the inner terminal of the lower right-hand repeating-coil winding, but the upper w nding oi' relay 130 is left open on ac- 111 of the fact that relay 129 is operated. Line relay 130, therefore, falls back and at its upper contacts opens the loop extending to the switch train including the switch S re sulting in the release of this'switch train. At its lower armature, relay 130 opens the circuit of relay 131 with the result that relay 131 shortly falls back and renders the trunk line TL idle to the connector such as D by removing ground potential from release trunk conductor 108. There is an incidental operation of relay 132 in the repeater and of relay 206 of the repeater R during release, but this has no effect 011 the releasing operation. Relay 124 falls back and permits relay'129 to restore.

Night calls to the P. A. X.

At night it is'usual for a watchman or some other person to be on the premises wherein the I. A. X. located after the other employees have gone home. in order that calls incoming to the P. A. may be answered by him at l; s telephone in the usual manner, the trunlr line TL is provided with a night jack NJ into which one plug of a special night cord may be inserted, the other plug of this cord being inserted into the regular jack of the line associated with the night telephone. The special cord is arranged so that ground potential is suppliedto the sleeve ol the night jack NJ. The upper main spring of the night jack disconnects the mechanical signal MS, which is used by the day operator as an indication of the busy or idle condition of the trunk, and it places ground on the release trunk conductor211 so as to render this trunk busy to the selectors such as S Now, when a call comes in over the trunk lineTL, relay 202 operates over conductors 150 and 151, when the transfer relay 112 in the repeater R operates upon the seizure of the repeater by connectors such as C, and relay 201 operates as a result of the operation of relay 202. the ringing current is received, ring-up relay 20? operates as hereinbc'fore described and locks itself at its lower contacts to conductor 206 through contacts of cut-off relay 203. At this time, since the sleeve of the night jack NJ is grounded owing to the fact that a plug at the night cord is placed therein a circuit is closed at the upper contacts of relay 207 *for the night ringing relay 20S. telay 208fopcrates and atits lower armature connects the common ringing lead to conductor 215, while at its upper armature it connects conductor 210 to battery by way of the upper winding of relay 209 so as to serve as a return circuit for the ringing current. At its inner contacts, relay 208 disconnectsconductors 210 and 215' from the corresponding re peating-coil windings, so as to prevent the ringing current from going baclr into the repeating coil." Ringing current is now applied to the called line from the local ringing source and when the call is answered at the night telephone, the ring-cut-ol'l' relay 209 operates over the called line by means of its upper winding and closes alocking'circuit for its lower windin to conductor 216 at its inner lower contacts. At its upper and lower ar matures, relay 209 disconnects conductors 210 and 215 from its own upper winding and from the ringing lead, respectively, and extends them to theright-hand repeating-coil windings again so as to complete the talking circuit lone relay 2041 now pulls up over the line h en connected by the night cord to the night ack NJ and closes a circuit for release relay 205 which operates and closes a circuit for cut-off relay 203. Cut-off relay 203 operates and disconnects relay 202 whereupon the ringcut-off operation in the main exchange is performed in the usual manner. The conversation may now proceed;

When the conversation has been terminated, the local called subscriber replaces his receiver whereupon relay 204 falls back and allows the circuit to clear out in the hereinbefore described manner.

It may be pointed out that an outgoing call from the P. A. X. may be made at any time at night over another one of the trunk lines in groups through the regular selectors such as S and in the same way that a daytime call is made.

What is claimed is:

1. In a telephone system, a trunk line extending from a first exchange to a second exchange and accessible to connector switches in the first exchange, said trunk line being divided into two inductively coupled sections, circuit arrangements associated with said connector switch for supplying ringing current to the first section of said trunk line, means responsive to the seizure of said trunk line by said connector switch for setting up current flow over the trunk line, means at the distant end of the trunk line "for signaling a called party, and means efto apply ringing current thereto, and means responsive to the response of a called party on said line for stopping the flow of direct currcntthereover, and means responsive to the stopping of the flow of direct current over said line for stopping the application of ringing current thereto.

3. In a telephone system, a trunk line extending from a first automatic exchange to a second automatic exchange and terminating in a repeater in the second exchange, means for seizing the trunk line in the first exchange and for setting up a current flow thereover, a train 01 automatic switches in the second exchange .operated from said repeater responsive to interruptions in the current flow over said trunk line, means in said repeater eiifectivc after the connection is set up for locking the connection so that it is held up independent of further current flow over said trunk line during conversation, said means including a diiferential relay having one winding energized in a local circuit and the other winding connected to said trunk line, and means elfective when the calling subscriber replaces his receiver for applying a current source to the originating end of said trunk line to deenergize said differential relay by sending current through the line winding thereof, and circuit connections such that the connection in the second exchange is released responsive to the deenergization of said differential relay.

4. In a telephone system, a main exchange, a branch exchange, trunk lines extending from the main exchange to a manual switchboard in the branch exchange, final connecor switches in the main exchange having access to said trunk lines, circuit connections for causing a current flow over one of said trunk lines after a connection has been extended thereto by a connector switch and while the connector switch is applying ringing current to the trunk line, circuit connections in the branch exchange for stopping the current flow over said trunk line when the manual operator at said switchboard responds to the call, and means in the main exchange for discontinuing the application of ringing current responsive to the stopping of said current flow.

5. In a telephone system wherein trunk lines extend from an automatic main exchange to a combined automatic and manual private branch exchange and wherein the trunk lines are accessible in the main exchange to final connectors arranged to apply ringing current, means in the private branch exchange for signaling the operator thereat responsive to ringing current when a trunk line is seized by a connector in the main exchange, and means for carrying on all required operations over said trunk line and for maintaining the trunk line disconnected at both ends from ground connections during conversation.

In witness whereof, I hereunto subscribe my name this 30th day of November, A. D.

CLARENCE E. LOMAX.

In witness whereof, lv hereunto subscribe my name this 30th day of November, A. D.

JOHN H. VOSS. 

